Refrigerating apparatus with overload control



' June 4, 1957 F. l. RATAICZAK ETAL REFRIGERATING APPARATUS WITHOVERLOAD CONTROL 2 sne'ets-sneet 1 Filed April 1, 1953 June 1957 F. l.RATAICZAK ETAL 2'794323 REFRIGERATING APPARATUS WITH OVERLOAD cou'raor.

Filed April 1. 1.95: 2 Sheets-Sheet 2 F lg. 3

' 5 42 Fig. 5 I -E I Y [7 4 26 44 40 I Attorney Unite Dayton,

Francis 1. Rataiczak and Harold C. Pearson,

Ohio, assignors to General Motors Corporation, troit, Mich, acorporation of Delaware Application April 1, 1953, Serial No. 346,242 2Claims. (Cl.'62-4) This invention relates to refrigerating apparatus andmore particularly to a construction and arrangement for preventingdangerous or excessive head pressures.

When a leak develops in the evaporator of a refrigerating system, minutequantities of moisture-laden air are admitted to the interior of thesystem and the accumulation of moisture resulting therefrom sometimescauses frost to form in the restrictor so as to completely block theflow of refrigerant from the condenser into the evaporator. When thishappens, the compressor will pull in additional quantities of air intothe system at a rate which is insufficient to cause overloading of thecompressor even though the head pressure becomes excessive. It is anobject of this invention to provide a simple arrangement for stoppingthe compressor before dangerouslyhighhead pressures can develop.

More particularly, it is an object of this invention to provide apressure operated valve which serves to load the compression chamberwith a larger volume of high pressure gas so as to still the compressorand thereby bring into operation the usual motor overload protectors forde-energizing the compressor motor.

It is another object of this invention to provide a safety valve meanswhich will not result in the loss of any of the refrigerant charge whenthe valve opens.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Figure 1 is a fragmentary vertical sectional view showing a compressorprovided with the invention;

Figure 2 is a sectional view taken substantially on line 22 of Figure 1;

Figure 3 is a sectional view taken substantially on line 33 of Figure 1;

Figure 4 is a fragmentary sectional view on an enlarged scale showingthe construction of the relief valve; and,

Figure 5 is an elevational view largely diagrammatic showing arefrigerating system embodying the invention.

For purposes of illustrating the invention, a refrigerating system ofthe type used in a household refrigerator has been shown whereas certainaspects of the invention are equally applicable to other types ofsystems.

Referring now to Figure 5 of the drawing wherein there is shown acomplete refrigerating system, reference numeral designates a sealedmotor-compressor unit which is adapted to discharge compressedrefrigerant into a condenser 12 from whence condensed refrigerant is fedto an evaporator 14 through a fixed restrictor 16. The evaporator 14 isintended to designate a conventional evaporator of the type used forrefrigerating the frozen food storage compartment in a householdrefrigerator. A second evaporator 18 is connected in series with theStates Patent 0 ice evaporator 14 and is intended to designate aconventional plate type evaporator of the type commonly used in the mainfood storage compartment.

The refrigerating system is of the well-known type in which the secondevaporator 18 is defrosted during each ofi cycle of the compressor. Therefrigerant vaporized in the evaporators is returned to themotorcompressor unit 10 through the return line 20 which leads to thecompressor inlet port 22 in accordance with standard practice.

A thermostat 24 mounted on the plate evaporator 18 is adapted to startand stop the motor-compressor unit by opening and closing the switch 26located in the main motor circuit. This thermostat is of the wellknowntype which opens the circuit at approximately 0 F. and closes thecircuit at a temperature slightly above freezing. A conventional motoroverload protector 30 is provided as shown for interrupting the flow ofcurrent to the compressor motor in the event that the compressor motorbecomes overloaded. Since thermostatic control switches and overloadprotector switches of this type are well known in the art, they will notbe described in further detail. Reference is hereby made to Clark Patent2,447,488 for a disclosure of one type of motor overload protectorswitch which may be used.

It has been found that plate type evaporators which are defrosted duringeach off cycle sometimes develop frost blisters adjacent the edges ofthe plate which eventually increase in size so as to produce a leak inthe evaporator. 'Since the evaporator pressure then falls belowatmospheric pressure air will enter the system through the leak. Thisair will introduce moisture into the system which tends to freeze, inthe restrictor line 16 leading from the condenser to the evaporator.When this occurs, it is obvious that the flow of refrigerant into theevaporator will completely stop but minute quantities of air will bepulled into the suction side of the compressor and thereby verygradually build up the head pressure in the system. In view of the factthat the amount of air leaking into the system is usually very small,the compressor does not become overloaded even though the head pressurebecomes dangerously high.

In the system shown for purposes of illustrating the invention, thecompressor is a rotary compressor having a main cylinder element 32mounted between end plates 34 and 36 in accordance with standardpractice. As shown in Fig. 2, a divider block 37 separates the inletport 22 from the conventional outlet port 38. The outlet port 38connects to the line 40 (see Fig. 5) which leads to a small heatexchanger 42 which serves to remove some of the heat from the fluiddischarged from the compressor before returning the compressed fluid tothe interior of the motor-compressor housing designated by the referencenumeral 44. Reference character 46 designates the usual drive shaftwhich has an eccentric portion cooperating with the usual impeller 48. Amotor rotor 50 is secured to the upper end of the drive shaft 46 and isdisposed to operate within the motor stator 52 located in the upperportion of the housing 44 in accordance with conventional practice.

A safety valve assembly has been provided in the upper end plate 34 forartificially loading the compressor at excessively high head pressuresso as to cause the usual thermal overload protector 30 to come intooperation and stop the compressor.

As best shown in Figures 1 and 4 of the drawing, the safety valveassembly is mounted in a passage 62 provided in the upper end plate. Theupper end 65 of this passage communicates with the interior of themotorcompressor housing 44 into which the compressed refrigerantdischarges. The lower end of the passage communicates with thecompression chamber .64 adjacent the inlet 22 so that upon downwardmovement of the valve element 63 in response to excessive head pressure,

.high pressure gas is fed 'directly' into the" compression chamber so asto 'fill thesame with this high pressure gas. The motor lacks'thenecessary powerto further compress this high pressure gas With theresult that the The valve consists of a plunger 63 which is biased intosealing engagement with the valve seat 66 by means of a coil spring 68.The lower end of the coil spring .68 is held in place by means ofthethreaded insert 70. .iThe insert 70 is provided with a screw-driver slot72 vwhich intersects a central gas passage 74 provided in thelower wallof the insert -70; v .the bottom end of the insert 70 is beveled asindicated It will be noted that at 76. It will also be noted from- Figs.3 and 4 that the insert 70 'is primarily located above the cylinder ele'ment.32.so as to prevent the insert 70 from striking the impeller 48 inthe event that the insert should become loose and start movingdownwardly. It will also be noted that one edge of the beveled portionof the insert 70 overlies the compression chamber. By virtue of thisarrangement the screw-driver slot 72 connects the central passage 74with the compression chamber through frigerant flow connections betweensaid compressor, condenser. anie apora c a electric to for Op r ioverload protector 30 comes into operationto stop the compressor beforeany further increasing in the head .pressure may occur. o

so I

said compressor, a source of electrical energy, means connecting saidmotor to said source of electrical energy including a thermal overloadresponsive switch interrupting the flow of electricity to said motor inresponse to an overload on said motor, means forming a bypass from theoutlet of said compressor to said compression chamber, and a valve insaid by-pass operable to admit high pressure refrigerant from the outletof said compressor to said compression chamber so as to overload saidcompressor in response to excessive outlet pressures.

2. In combination, a housing, a motor-compressor assembly disposedwithin said housing, means introducing a fluid to be compressed intosaid compressor, said compressor having an outlet, means directing thefluid discharged through said outlet into said housing, said compressorincluding means forming a compression chamher having a passage its onewall connecting the interior of said housing to said compressionchamber, and

a pressure responsive valve within said passage operable to admit fluidfrom said housing to said compression chamber-in response to apredetermined increase of pressure Within said housing.

References Cited in the file of this patent UNITED STATES PATENTS1,792,027 Parker Feb. 10, 1931 2,117,468 Wolcott May 17, 1938 2,278,832Cornelius Apr. 7, 1942 7 2,290,984 McCoy July 28, 1942 2,314,591McCormack Mar. 23, 1943 2,481,605 McLeod Sept. 13, 1949 2,548,799Johnson et a1. Apr. 10, 1951 2,552,633 Johnson May 15, 1951

